The term multi-chamber tube is used herein to denote a packaging tube which includes at least two chambers for keeping packaged items or substances separately from each other. In the case of a two-chamber tube the chambers are formed by a divider wall or partition which is arranged within the body portion of the tube and which, starting from a bottom closure seam which extends perpendicularly to the longitudinal axis of the tube, passes in the longitudinal direction through the tube body portion with, arranged thereon, a tube head and a tube nozzle for discharge of the tube contents. In that case, the partition with its outer edges can be in engagement with the bottom closure seam, the internal peripheral surface of the tube body portion, an internal shoulder surface and the internal peripheral surface of the nozzle on the tube head. The foregoing reference to being in engagement means for example that the partition can simply bear with its outer longitudinally directed edges against the internal surfaces of the tube body portion, can bear thereagainst under a spring force or can be connected to the internal surface for example by welding or adhesive. If the partition is divided into a part in engagement with the tube body portion, which can thus be called the tube body portion part, and a part which is in engagement with the tube head, which can thus be called the tube head part, then a transverse edge of the tube body portion part, which extends in the diametral direction, can be connected as by welding to the bottom tube closure seam while the other edges are only in a condition of simply bearing against the respective surface, this being taken as an example to show that the tube body portion part including the transverse edge and the head part can respectively be in engagement with the walls of the tube body portion and the tube head in the same or different ways in accordance with the above-described possible options in a portion-wise manner. The choice of a variant out of the large number of different forms of connection between the partition and the tube body portion is determined to a considerable extent by the substances to be packaged. If for example two technical greases which do not chemically react with each other are to be simultaneously discharged from a two-chamber tube, then it is sufficient to provide a two-chamber tube with an inserted partition, the edges of which simply bear against the internal surface of the tube and the tube head. If in contrast packaged substances which are chemically reactive with each other are intended to be packaged and discharged simultaneously from the packaging tube, then this usually entails using multi-chamber tubes whose partition is fixedly connected for example by welding to the internal surface of the tube, more specifically at the transverse bottom closure seam, at the tube body portion, at the tube head with shoulder and at the tube nozzle.
Tubes of the configuration referred to herein, and more particularly their tube body portions for example, are made from plastic sheets or films comprising plastic materials which are suitable for packaging purposes. These can be polyethylenes, both of high and low density, polypropylenes, ethylene and propylene copolymers and polyethylene teraphthalates. The films or sheets can be in the form of laminates in which a gas-barrier layer of ethylene vinyl alcohol, polyamide or polyvinylidene chloride, or a metal film or sheet, preferably aluminum, is accommodated between layers of polyethylene, polypropylene or copolymers. The gas-barrier layer prevents the loss of certain ingredients of the packaged substances which, having passed into the gaseous phase, would diffuse through plastic films or sheets without a barrier layer. The barrier layer on the other hand also prevents gases from the environment outside the tube from having access to the packaged substances therein. Production of the tube body portions of plastic film or sheet is effected by shaping the film or sheet to form a tube body portion and welding the longitudinal edges of the film or sheet together.
Three procedures have proven successful in terms of fitting tube body portions with tube heads. In a first procedure a prefabricated tube head is connected to the tube body portion. A second procedure involves forming a tube head by injection molding on the tube body portion while a third procedure involves forming the head on the tube body portion by press shaping.
The plastic material for the heads corresponds to that of the films or sheets, or that of the outer cover layers of a laminate. In regard to the material for partitions, there is a wide range of different materials available; the materials that can be adopted, depending on the packaged substance, include papers, lined papers and plastic materials and also laminates, in which respect, in the case of plastic materials, they must be matched to the plastic materials of the tube body portions and heads if a partition is to be fixedly connected to a tube body portion and head, for example by welding.
The design of multi-chamber tubes, choice of material and production processes have advanced to such an extent that tubes are available, which may satisfactorily perform the functions attributed thereto such as keeping packaged substances separately and providing durability or shelf life of the packaged substances, but the discharge thereof may give rise to certain problems.
At this point consideration will be given as an analogy to extrusion devices intended for the production of items, starting for example from plastic material masses of a pasty or dough-like constitution. Continuous reproducibility of the extruded products depends to a substantial extent, having regard to the constancy involved, on the setting values at the apparatus, for example the temperature, the pressure and the uniformity of discharge of the material, that is to say the extrusion characteristics, which can also be referred to as ‘metering capability’, or, for the sake of brevity, ‘metering’, of the apparatus.
If now a single-chamber or multi-chamber tube is compared to an extrusion apparatus, it will be clear that uniformity of the discharge of material therefrom can scarcely be achieved, as a result for example of unavoidably fluctuating pressure loadings on the packaged substance in the tube body portion. This means that the characteristics which, on the basis of the above-mentioned analogy of extrusion devices, can be called the extrusion characteristics, of packaging tubes which are otherwise of a satisfactory design configuration in terms of the regular use thereof are unsatisfactory. The foregoing expression uniformity of the discharge of material means for example the discharge of a uniform amount per unit of time or emission of a mass consisting of two components, while maintaining for example the same proportions in terms of quantity and component. The fluctuating pressure loadings result from the pressure loadings which can be applied to the tube by thumbs and fingers of a human hand to respective substantially oppositely disposed surfaces of the wall of the tube body portion and which vary in terms of magnitude from one extrusion or material-discharge operation to another or which can build up or decrease during one extrusion or discharge procedure. The degrees to which the chambers are filled with their respective substances also exert a further and not inconsiderable influence on the extrusion characteristics. With a low level of filling of the chambers and when the loading begins, more specifically it is not possible to predict the flow direction, that is to say towards the head or towards the bottom closure seam of the tube, for the packaged substance therein. For example, in the case of multi-chamber tubes, the packaged substance in one chamber can initially move in opposite relationship to that in another chamber, and that adversely affects the required uniformity of the discharge of material.
The inability, in normal handling of the tube, to repeatedly discharge uniform amounts of packaged substance out of a single-chamber tube or a multi-chamber tube is often referred to in the language in the art for the sake of brevity as ‘metering insufficiency’. This counts as a factor in particular against the multi-chamber tube as an emptiable container or packaging means for packaged substances which, stored therein in the form of components, are dispensed in combination only upon use in quantitative proportions which are definitively metered. Packaged substances involving that form of dispensation thereof are known in many different respects for technical, dental-hygiene, cosmetic and up to pharmaceutical purposes. At the present time they are predominantly packaged in component-wise manner in separate containers, in which respect calibration devices for equal quantitative metering are added to such containers.
This limited utility of tubes of the described configuration is found to be a further disadvantage.